DBRefs are supposed to be informal, allowing arbitrary properties in addition to $ref, $db, and $id. The database stores them correctly, but the JavaScript shell silently drops them from output. This can be shown by importing data containing an "extra" property, performing a search for records with this set to 1 (demonstrating that the database handles it correctly), and then printing the value of "extra".

To reproduce:

> echo '{ otherobj :

{ "$ref" : "othertable", "$id" : "notimportant", extra : 1 }

}' > test.json
> mongoimport -h localhost -d test -c test test.json
> mongo localhost/test --eval "printjson(db.test.findOne(

{\"otherobj.extra\":1}

).extra)"

The last line should return "1", it currently returns "null".